In known stepper motors having a plurality of windings the stepping motion is produced by energisation of the windings in a particular sequence. For example, a stepper motor may have in one revolution two hundred main stepping positions which are defined by selectively energising pairs of windings. A smoother motion for such a motor may be attained by dividing each main stepping position into a number of smaller steps by decreasing the energisation of the windings in a corresponding number of stages. It may be desirable that the steps of a stepper motor are as equal as possible, but owing to non-linearity in the motor, equal increments of current in the windings of the motor might not produce correspondingly equal steps.